1. Technical Field
The present disclosure relates to the attachment of surgical sutures to surgical needles. In particular, the disclosure relates to a method for the attachment of surgical needles to collagenous "catgut" surgical sutures to provide a combined surgical needle-suture device possessing controlled suture release characteristics.
2. Background of Related Art
For many years, surgeons have employed needle-suture combinations in which a suture or ligature is attached to the shank end of a needle. Such needle-suture combinations are provided for a wide variety of monofilament and braided suture materials, both absorbable and non-absorbable, e.g., catgut, silk, nylon, polyester, polypropylene, linen, cotton, and absorbable synthetic materials such as polymers and copolymers of glycolic and lactic acids.
Needle-suture combinations fall into two general classes: standard needle attachment and removable or detachable needle attachment. In the case of standard needle attachment, the suture is securely attached to the needle and is not intended to be separable therefrom, except by cutting or severing the suture. Removable needle attachment, by contrast, is such that the needle is separable from the suture in response to a force exerted by the surgeon. Minimum acceptable forces required to separate a needle from a suture for various suture sizes are set forth in the United States Pharmacopeia (USP XXII 1990). The United States Pharmacopeia prescribes minimum individual pull-out forces and minimum average pull-out forces as measured for five needle-suture combinations. The minimum pull-out forces for both standard and removable needle-suture attachment set forth in the United States Pharmacopeia are hereby incorporated by reference.
One typical method for securely attaching a suture to a needle involves providing a cylindrical recess in the shank end of a needle and securing a suture therein. For example, U.S. Pat. No. 1,558,037 teaches the addition of a cement material to such a substantially cylindrical recess to secure the suture therein. Additional methods for bonding a suture within a needle bore are described in U.S. Pat. Nos. 2,982,395 (adhesives) and 3,394,704 (bonding agents). Alternatively, a suture may be secured within an axial bore in a needle by swaging the needle in the region of the recess, see, e.g. U.S. Pat. No. 1,250,114. Additional prior art methods for securing a suture within a needle bore include expansion of a catgut suture through the application of heat (U.S. Pat. No. 1,665,216), inclusion of protruding teeth within the axial bore to grasp an inserted suture (U.S. Pat. No. 1,678,361) and knotting the end of the suture to be inserted within the bore to secure the suture therein (U.S. Pat. No. 1,757,129).
Methods of detachably securing a suture to a needle are also well known. For example, a prevailing controlled release needle-suture attachment is swaged or crimped described in U.S. Pat. Nos. 3,890,975, 3,980,177, 4,060,885 and 4,072,041. In accordance with the methods taught by these patents, a suture tip is inserted into a drilled end of the needle and the needle end is swaged to engage the suture to effect needle-suture attachment.
The methods described in the above patents for forming detachable needle suture combinations are intended to provide minimum pull-out forces within a desired range. With suture materials that are stable when packaged or stored, the pull-out value remains within the targeted pull-out range. However, certain materials, such as catgut, have a tendency to expand or swell when exposed to moisture, such as conditioning fluid typically provided in the catgut suture package. As a consequence, this expansion adversely increases the pull-out force required to detach the suture from the needle.
In an effort to account for the increase in dimension of fluid swellable suture materials upon exposure to moisture and, thus, an increase in the force required to detach the suture from the needle, attempts have been made to initially decrease the swaging force during needle-suture attachment so that the pull out force subsequent to packaging (and, hence after any swelling) would be within an acceptable range. However, this approach is not feasible since the attachment force prior to packaging must be lowered to unacceptable levels. Consequently, the decreased attachment force results in the sutures having a tendency to prematurely detach during subsequent processing steps, such as packaging, thereby requiring excessive special handling.
Other attempts to accommodate for suture swelling during storage include providing a needle end having an increased dimensioned recess or axial opening to accommodate subsequent expansion of the gut suture material during storage. see, e.g., U.S. Pat. Nos. 3,924,630 and 4,124,027. However, with the methods suggested in these two patents, the suture in its dry non-swollen condition, i.e., prior to packaging in a conditioning fluid, is subject to displacement within the enlarged recess of the needle and, consequently, is prone to prematurely detach from the needle.
Accordingly, the present disclosure is directed to a method for attaching a fluid swellable suture material to a surgical needle whereby the attachment formed meets the minimum pull-out forces for detachable needle suture devices as set forth in the United States Pharmacopeia.